Electronic component and method for manufacturing electronic component

ABSTRACT

A method for manufacturing an electronic component includes a step of preparing a plurality of electrical elements, a step of preparing a base including a plurality of boards on which the plurality of electrical elements are to be mounted, respectively, a step of forming a resin on the base, a step of pressing the plurality of electrical elements against the resin to join portions of side surfaces of the plurality of electrical elements to the resin, a step of grinding the plurality of electrical elements to thin the plurality of electrical elements, and a step of dividing the base to form the plurality of board into individual pieces.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic component and a methodfor manufacturing an electronic component, and in particular, relates toa method for manufacturing an electronic component, including a step ofgrinding electrical elements or boards, and an electronic componentmanufactured by the manufacturing method.

2. Description of the Related Art

Japanese Unexamined Patent Application Publication No. 2006-100587discloses the following method for manufacturing a solid-state imagingdevice. First, grooves of a predetermined depth are formed in a waferhaving a plurality of solid-state imaging elements formed on a frontsurface thereof, so as to define each solid-state imaging element. Then,as shown in the left-hand portion of FIG. 3, the wafer 60 and a board 50are joined to each other via spacers 70 which enclose the solid-stateimaging elements. After the wafer 60 and the board 50 are joined to eachother, the wafer 60 is ground on a back side thereof to form thesolid-state imaging elements into individual pieces. Then, the board 50is diced to produce individual solid-state imaging devices.

Japanese Unexamined Patent Application Publication No. 2001-332654discloses the following method for manufacturing a module including anelectrical element. First, an electrical element 81 having an electricalelement formed on a front surface thereof is flip-chip bonded onto awiring board 90 via bumps 82 and sealed with a thermosetting resin 100.Then, the back surface of the electrical element 81 and thethermosetting resin 100 are ground simultaneously to reduce the height.

In the solid-state imaging device manufacturing method disclosed inJapanese Unexamined Patent Application Publication No. 2006-100587,during grinding of the wafer 60, a physical load is applied from agrinding stone to the wafer 60 not only in the vertical direction butalso in the horizontal direction. When the grinding of the wafer 60progresses and the solid-state imaging elements are divided to defineindividual pieces, a sufficient retaining force is not applied to eachsolid-state imaging element in the horizontal direction, and thus theelectrical elements are likely to be separated from the spacers 70 dueto the horizontal load from the grinding stone, as shown in FIG. 3 (theright-side diagram).

In the electrical element-included module manufacturing method disclosedin Japanese Unexamined Patent Application Publication No. 2001-332654,when the electrical element 81 is ground, not only the electricalelement 81 but also the thermosetting resin 100 are groundsimultaneously. Thus, due to a horizontal physical load during thegrinding, the interface between the side surface of the electricalelement 81 and the thermosetting resin 100 is likely to be separated toproduce a gap (A in FIG. 4). When a gap is produced between the sidesurface of the electrical element 81 and the thermosetting resin 100,moisture and the like enter the gap and hence the weather resistance ofthe electrical element-included module deteriorates.

SUMMARY OF THE INVENTION

In view of the problems described above, preferred embodiments of thepresent invention provide a method for manufacturing an electroniccomponent that prevents separation of an electrical element from amember which retains or seals the electrical element, duringmanufacturing of the electronic component; and an electronic componentmanufactured by the manufacturing method, which has excellent mechanicalstrength and weather resistance.

According to a preferred embodiment of the present invention, anelectronic component includes an electrical element including first andsecond principal surfaces opposed to each other, side surfacesconnecting the principal surfaces, and a functional portion provided onthe first principal surface; a board including first and secondprincipal surfaces opposed to each other and side surfaces connectingthe principal surfaces, the first principal surface being arranged so asto face the first principal surface of the electrical element; and aresin interposed between the first principal surface of the electricalelement and the first principal surface of the board. The secondprincipal surface of either one of the electrical element or the boardis a ground surface which has been subjected to grinding, and the resinincludes a joining portion which covers a portion of the side surfacesof either one of the electrical element or the board and which isseparated from the ground surface.

In a preferred embodiment of the present invention, in the electroniccomponent, the resin includes a hollow portion above the functionalportion of the electrical element.

In another preferred embodiment of the present invention, in theelectronic component, the electrical element is a surface acoustic waveelement.

According to a further preferred embodiment of the present invention, amethod for manufacturing an electronic component includes the steps ofpreparing a plurality of electrical elements; preparing a base includinga plurality of boards on which the plurality of electrical elements areto be mounted, respectively; forming a resin layer on the base; pressingthe plurality of electrical elements against the resin layer to joinportions of side surfaces of the plurality of electrical elements to theresin layer; grinding the plurality of electrical elements to thin theplurality of electrical elements; and dividing the base to form theplurality of boards into individual pieces.

According to another preferred embodiment of the present invention, amethod for manufacturing an electronic component includes the steps ofpreparing a first base on which a plurality of electrical elements areformed; forming a resin layer on the first base; preparing a second baseincluding a plurality of projections on a front surface thereof;pressing the plurality of projections against the resin layer to joinportions of side surfaces of the plurality of projections to the resinlayer; grinding a back surface of the second base to form the pluralityof projections into individual pieces to form a plurality of boards; anddividing the first base to form the plurality of electrical elementsinto individual pieces.

In a preferred embodiment of the present invention, the method furtherincludes the step of providing a plurality of recesses in the resinlayer after the resin layer is formed.

In another preferred embodiment of the present invention, in the method,the resin layer preferably is a photosensitive resin, for example.

According to various preferred embodiments of the present invention,during manufacturing of an electronic component, separation of theelectrical element from a member which retains or seals the electricalelement is reliably prevented. In addition, an electronic componenthaving excellent mechanical strength and reliability can be realized.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1I are diagrams showing each step of a method formanufacturing an electronic component according to Preferred Embodiment1 of the present invention.

FIGS. 2A to 2H are diagrams showing each step of a method formanufacturing an electronic component according to Preferred Embodiment2 of the present invention.

FIG. 3 is a diagram (part 1) showing a problem of an existing method formanufacturing an electronic component.

FIG. 4 is a diagram (part 2) showing a problem of an existing method formanufacturing an electronic component.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed. It should be noted that like or corresponding portions aredesignated by the same reference characters and the description thereofmay not be repeated.

It should be noted that in the preferred embodiments described below,when a number, an amount, and the like are mentioned, the scope of thepresent invention is not necessarily limited to the number, the amount,and the like unless otherwise specified. In addition, in the preferredembodiments described below, each component is not necessarily essentialfor the present invention unless otherwise specified.

Preferred Embodiment 1

FIGS. 1A-1I are diagrams showing each step of a method for manufacturingan electronic component according to Preferred Embodiment 1. Each stepwill be described with reference to FIGS. 1A-1I.

First, as shown in FIG. 1A, a wafer 11A (for example, having a thicknessof about 250 μm) is prepared in which functional portions, wires, andpad electrodes of a plurality of electrical elements 11 are formed on afront surface thereof by a thin film microfabrication technique. Next,as shown in FIG. 1B, stud bumps 12 made of gold (Au) are formed on thepad electrodes of the electrical elements 11. Further, as shown in FIG.1C, the wafer 11A is diced to divide the electrical elements 11 intoindividual rectangular chips.

Meanwhile, as shown in FIG. 1D, a base 20A including a plurality ofwiring boards 20 on which the electrical elements 11 are to be mountedis prepared. Next, as shown in FIG. 1E, a photosensitive resin 21 isapplied to a front surface of the base 20A. Then, a plurality ofrecesses are formed in the resin 21 by a photolithographic technique.Here, the recesses of the resin 21 are opened such that land electrodescorresponding to the pad electrodes of the electrical elements 11 areexposed. In addition, the openings of the recesses are formed so as tobe preferably smaller than the electrical elements 11.

As shown in FIG. 1F, the electrical elements 11 which are made into theindividual pieces in the step shown in FIG. 1C are flip-chip bonded(FCB) onto the base 20A. Specifically, the electrical elements 11 arearranged so as to seal the openings of the recesses of the resin 21 andsuch that the stud bumps 12 formed on the pad electrodes of theelectrical elements 11 are located above the land electrodes of the base20A. Then, back surfaces of the electrical elements 11 are pressedtoward the base 20A while ultrasonic vibrations are applied thereto by abonding tool. By so doing, the pad electrodes of the electrical elements11 are connected to the land electrodes of the base 20A via the studbumps 12. In addition, the resin 21 is not cured at that time, and thusthe electrical elements 11 can be dug into the resin 21. Thus, the resin21 moves around to the side surfaces of the electrical elements 11.

Next, as shown in FIG. 1G, the resin 21 which is also thermosetting isheated at a temperature of about 300° C. to about 400° C., for example,to be cured. By so doing, portions of the electrical elements 11 arejoined to the resin 21, whereby the electrical elements 11 are retainedby the resin 21. Moreover, as shown in FIG. 1H, the back surfaces of theelectrical elements 11 are ground such that the electrical elements 11are thinned to desired thicknesses, for example, about 150 μm. Thethicknesses of the electrical elements 11 are preferably smaller, butthe grinding is ended before a grinding stone reaches the resin 21.Thus, the resin 21 is not ground.

Finally, as shown in FIG. 1I, the base 20A is diced together with theresin 21 to divide the wiring boards 20 into individual pieces, wherebya plurality of electronic components are completed.

Each of the electronic components completed thus preferably includes theelectrical element 11 including first and second principal surfacesopposed to each other, side surfaces connecting the principal surfaces,and the functional portion provided on the first principal surface; thewiring board 20 including first and second principal surfaces opposed toeach other and side surfaces connecting the principal surfaces, thefirst principal surface being arranged so as to face the first principalsurface of the electrical element 11; the resin 21 interposed betweenthe first principal surface of the electrical element 11 and the firstprincipal surface of the wiring board 20. The second principal surfaceof the electrical element 11 is a ground surface which has beensubjected to grinding. The resin 21 includes a joining portion whichcovers a portion of the side surfaces of the electrical element 11 andwhich is separated from the ground surface. In addition, the resin 21includes a hollow portion which seals the functional portion of theelectrical element 11.

It should be noted that each electrical element 11 may be a surfaceacoustic wave element, a piezoelectric thin-film element, a thin-filmcircuit element, a semiconductor element, or another element.

In this preferred embodiment, as the material of the wiring boards 20,ceramics such as alumina are typically considered, but monocrystals suchas Si, LiTaO3, LiNbO3, and crystal and resins such as glass epoxy resinscan also be used. It should be noted that in the present invention,bases for the electrical elements are not limited to the above-describedwiring boards, and boards which serve as electrical elements may beused, for example.

Further, when, for example, a photosensitive resin such as aphotosensitive polyimide resin is used as the resin 21, patterningaccuracy of the recesses is improved, whereby the side surfaces of theelectrical elements 11 can more assuredly be protected. However, theresin 21 is not limited to the photosensitive resin, and a materialother than the photosensitive resin may be used to form recesses thereinby etching or other suitable process, for example.

It should be noted that an initial thickness (a state of FIG. 1E) of theresin 21 is adjusted such that the height of the resin 21 that movesaround to the side surfaces of the electrical elements 11 when theelectrical elements 11 are flip-chip bonded onto the boards 20 is lowerthan the sum of the final thickness of the electrical elements 11 afterthe grinding and the final height of the stud bumps 12 after the FCB.The initial thickness of the resin 21 is adjusted on the basis ofconditions of the viscosity of the resin 21, the number of rotations ofspin application, and the like.

Similarly, the conditions of the FCB are adjusted such that the finalheight of the stud bumps 12 is lower than the initial thickness of theresin 21. The conditions of the FCB mean the volume of each stud bump12, a load of the bonding tool, the ultrasonic wave conditions, and thelike.

According to the electronic components and the manufacturing methodthereof according to this preferred embodiment, the side surfaces of theelectrical elements 11, which are ground members, are retained by theresin 21, and thus separation of the electrical elements 11 due to ahorizontal physical load at grinding can be reliably prevented.

Further, the resin 21 retains only a region smaller than the thicknessof the electrical elements 11 after grinding, and thus is not ground.Therefore, the interfaces between the electrical elements 11 and theresin 21 are not separated due to a physical load at grinding.

Moreover, the hollow portion of the resin 21 is closed, and eachelectronic component has excellent weather resistance. In particular,this preferred embodiment is suitable for electrical elements 11 thatare surface acoustic wave elements in which a hollow portion is neededabove an interdigital transducer (IDT) which is a functional portion.

A summary of the above description is as follows. Specifically, themethod for manufacturing an electronic component according to thispreferred embodiment includes a step of preparing a plurality ofelectrical elements 11 (FIGS. 1A to 1C), a step of preparing a base 20Apreferably including a plurality of boards 20 on which the plurality ofelectrical elements 11 are to be mounted, respectively (FIG. 1D), a stepof forming a resin 21 as a “resin layer” on the base 20A (FIG. 1E), astep of pressing the plurality of electrical elements 11 against theresin 21 to join portions of the side surfaces of the plurality ofelectrical elements 11 to the resin 21 (FIGS. 1F and 1G), a step ofgrinding the plurality of electrical elements 11 to thin the pluralityof electrical elements 11 (FIG. 1H), and a step of dividing the base 20Ato form the plurality of boards 20 into individual pieces (FIG. 1I).

Preferred Embodiment 2

FIGS. 2A to 2H are diagrams showing each step of a method formanufacturing an electronic component according to Preferred Embodiment2. Each step will be described with reference to FIGS. 2A to 2H.

First, as shown in FIG. 2A, a wafer 31A is prepared in which functionalportions, wires, and electrode patterns 32 of a plurality of electricalelements 31, which electrode patterns 32 are to be pad electrodes, areformed on a front surface thereof by a thin film microfabricationtechnique. Next, a film type photosensitive resin is adhered to thefront surface of the wafer 31A, and a plurality of recesses are formedin the resin 33 by a photolithographic technique such that thefunctional portions of the electrical elements 31 are exposed as shownin FIG. 2B. At the same time, a plurality of grooves are formed in amatrix so as to define the recesses and such that, at least portions ofthe pad electrodes of the electrical elements 31 are exposed. Since thefilm type is used as the resin 33 as described above, the thickness ofthe resin 33 can precisely be controlled. As a film type resin, it isconsidered to use, for example, polyimide resins, epoxy resins, and thelike.

Meanwhile, as shown in FIG. 2C, a cap wafer 40 (for example, having athickness of about 350 μm) which is to be finally a cap of a package isprepared. Next, as shown in FIG. 2D, a front surface of the cap wafer 40is half-cut by dicing to form a plurality of grooves in a matrix. As aresult, a plurality of substantially rectangular projections 40A areformed on the front surface of the cap wafer 40 and defined by thegrooves 40B. Here, the projections 40A are formed so as to preferably belarger than the openings of the recesses of the resin 33. It should benoted that the depth of half-cutting preferably is about 125 μm, forexample.

As shown FIG. 2E, the wafer 31A and the cap wafer 40 are stacked to eachother at wafer level such that the projections 40A seal the openings ofthe recesses of the resin 33, and are joined to each other via the resin33 by thermal pressure bonding. At that time, by a load of the pressurebonding, the resin 33 is caused to enter portions of the grooves 40B ofthe cap wafer 40. In other words, the front surface side peripheralportions and side surfaces of the projections 40A are joined to theresin 33.

Next, as shown in FIG. 2F, the cap wafer 40 is ground to a thickness ofabout 100 μm, for example, to form the projections 40A into individualpieces. By so doing, the projections 40A become cap boards 40C whichseal the recesses of the resin 33.

Further, as shown in FIG. 2G, the cap boards 40C, the resin 33, and thewafer 31A are coated with a metal film by a film formation method suchas sputtering or plating. Then, a photoresist is applied onto the metalfilm and is pattern-formed by a photolithographic technique, and thenexternal terminals 50 are formed by an etching technique. Here, theexternal terminals 50 are connected to at least portions of the padelectrodes which are exposed from the grooves of the resin 33.

Finally, as shown in FIG. 2H, dicing is performed along the grooves ofthe resin 33 to divide the wafer 31A into pieces, whereby a plurality ofelectronic components are completed.

Each of the electronic components thus completed includes the electricalelement 31 including first and second principal surfaces opposed to eachother, side surfaces connecting the principal surfaces, and thefunctional portion provided on the first principal surface; the capboard 40C including first and second principal surfaces opposed to eachother and side surfaces connecting the principal surfaces, the firstprincipal surface being arranged so as to face the first principalsurface of the electrical element 31; and the resin 33 interposedbetween the first principal surface of the electrical element 31 and thefirst principal surface of the cap board 40C. The second principalsurface of the cap board 40C is a ground surface which has beensubjected to grinding. The resin 33 includes a joining portion whichcovers a portion of the side surfaces of the cap board 40C and which isseparated from the ground surface. In addition, the resin 33 includes ahollow portion which seals the functional portion of the electricalelement 31.

According to the electronic components and the manufacturing methodthereof according to this preferred embodiment, the side surfaces of theprojections 40A of the wafer 40, which is a ground member, are retainedby the resin 33, and thus separation of the cap boards 40C (theprojections 40A that are formed into the individual pieces) due to ahorizontal physical load at grinding can be prevented.

Further, the resin 33 retains only a region smaller than the thicknessof the cap boards 40C, and thus is not ground. Therefore, the interfacesbetween the cap boards 40C and the resin 33 are not separated due to aphysical load at grinding.

To summarize the above contents, the method for manufacturing anelectronic component according to this preferred embodiment includes astep of preparing a wafer 31A as a “first base” in which a plurality ofelectrical elements 31 are formed (FIG. 2A); a step of forming a resin33 as a “resin layer” on the wafer 31A (FIG. 2B); a step of preparingthe wafer 40 as a “second base” including a plurality of projections 40Aon a front surface thereof (FIGS. 2C and 2D); a step of pressing theplurality of projections 40A against the resin 33 to join portions ofthe side surfaces of the plurality of projections 40A to the resin 33(FIG. 2E); a step of grinding a back surface of the wafer 40 to form theplurality of projections 40A into individual pieces to form a pluralityof cap boards 40C (FIG. 2F); and a step of dividing the wafer 31A toform the plurality of electrical elements 31 into individual pieces(FIG. 2H).

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. An electronic component comprising: an electrical element includingfirst and second principal surfaces opposed to each other, side surfacesconnecting the principal surfaces, and a functional portion provided onthe first principal surface; a board including first and secondprincipal surfaces opposed to each other and side surfaces connectingthe principal surfaces, the first principal surface being arranged so asto face the first principal surface of the electrical element; and aresin interposed between the first principal surface of the electricalelement and the first principal surface of the board; wherein the secondprincipal surface of either one of the electrical element or the boardis a ground surface which has been subjected to grinding; and the resinincludes a joining portion which covers a portion of the side surfacesof either one of the electrical element or the board and which isseparated from the ground surface.
 2. The electronic component accordingto claim 1, wherein the resin includes a hollow portion above thefunctional portion of the electrical element.
 3. The electroniccomponent according to claim 2, wherein the electrical element is asurface acoustic wave element.
 4. A method for manufacturing anelectronic component, the method comprising the steps of: preparing aplurality of electrical elements; preparing a base including a pluralityof boards on which the plurality of electrical elements are to bemounted, respectively; forming a resin layer on the base; pressing theplurality of electrical elements against the resin layer to joinportions of side surfaces of the plurality of electrical elements to theresin layer; grinding the plurality of electrical elements to thin theplurality of electrical elements; and dividing the base to form theplurality of boards into individual pieces.
 5. The method according toclaim 4, further comprising the step of providing a plurality ofrecesses in the resin layer after the resin layer is formed.
 6. Themethod according to claim 5, wherein the resin layer is a photosensitiveresin.
 7. A method for manufacturing an electronic component, the methodcomprising the steps of: preparing a first base on which a plurality ofelectrical elements are formed; forming a resin layer on the first base;preparing a second base including a plurality of projections on a frontsurface thereof; pressing the plurality of projections against the resinlayer to join portions of side surfaces of the plurality of projectionsto the resin layer; grinding a back surface of the second base to formthe plurality of projections into individual pieces defining a pluralityof boards; and dividing the first base to form the plurality ofelectrical elements into individual pieces.
 8. The method according toclaim 7, further comprising the step of providing a plurality ofrecesses in the resin layer after the resin layer is formed.
 9. Themethod according to claim 8, wherein the resin layer is a photosensitiveresin.